A touch screen, as an input interface, provides a user with a more convenient means for inputting information than a keyboard or a mouse. Based on their working principles, the touch screens include a resistive type of touch screen, a capacitive type of touch screen, a surface acoustic wave type of touch screen, an infrared type of touch screen and etc. Until now, the resistive type of touch screen and the capacitive type of touch screen have been the ones that are commonly used.
The capacitive type of touch screens includes a surface capacitance touch screen, a projection self capacitance touch screen, a projection mutual capacitance touch screen, a single layer capacitance touch screen and etc. Among these touch screens, the projection mutual capacitance touch screen is prevailing for its merits of high sensitivity and multiple touches. A basic working principle of the projection mutual capacitance touch screen lies in detecting variations of signals on sides of detecting lines upon applying voltages on sides of driving lines. The driving lines determine X-axes of coordinates, and the detecting lines determine Y-axes of the coordinates. During the detection, the driving lines in the X-axes direction are scanned row by row, and upon scanning each row of the driving lines, the signal on each detecting line is read. Thus, all of the intersection points of rows and columns of the lines are scanned by a round of scanning, and X*Y signals are obtained accordingly. Such detection may determine the coordinates of a plurality of points, so that the multiple touches are implemented.
Conventionally, the commonly used projection mutual capacitance touch screen is a built-in projection mutual capacitance touch screen, which is driven based on time sequence, i.e. the driving of the display and the driving of the touch signal detection are implemented asynchronously. During a portion of a time period (for example, a time period of a frame), the scanning of the display driving signals is implemented, while the detecting of the touch signals is not implemented; and during the other portion of the time period, the detecting of the touch signals is implemented, while the scanning of the display driving signals is not implemented.
In such conventional driving based on time sequence, the time duration for detecting of the touch signals is short, and thus the frequency for detecting of the touch signals is high, which increases internal noises of the touch display device and deteriorates the display quality of the touch display devices.